1. Field of the Invention
The present invention relates to a zoom lens system, and an image pickup apparatus using the same. Furthermore, the present invention relates to an image pickup apparatus such as a digital camera and a video camera, which includes the zoom lens system and an image pickup element.
2. Description of the Related Art
In recent years, replacing a silver-halide film camera, a digital camera in which, an object is photographed by using a solid image pickup device such as a CCD (Charge Coupled Device) and a CMOS (Complementary Metal Oxide Semiconductor) has become a mainstream. Several categories of digital cameras in wide range from a high-function type for professional use to a compact popular type have been used.
Particularly, among digital cameras of popular type, a small size camera, particularly, a slim digital camera which can be accommodated easily in a pocket of clothes or a bag, and carried conveniently has been preferred.
Moreover, while a zooming ratio of about 3 of a photographic lens has been common, a camera of the magnification ratio of 3 or more, capable of taking pictures with a wide image angle for fulfilling needs over a wide range of a user has been sought.
A photographic lens which responds to such needs is required to be of a size such that a portability of the camera is not lost.
As a means for slimming of a camera, a so-called collapsible lens barrel in which, a lens barrel is pushed out from inside of a camera body in a picture taking state, and is accommodated inside the camera body at the time of carrying has been typical.
Generally, as a type of a zoom lens system which can be made compact, a zoom lens system of a negative precedence type in which, a lens unit having a negative refracting power is nearest to an object side has been known. Among these, a three-unit zoom lens system in which, a first lens unit having a negative refracting power, a second lens unit having a positive refracting power, and a third lens unit having a positive refracting power are disposed in order from the object side to an image side has been commonly known.
Since the zoom lens system of the negative precedence type has a refracting power arrangement of a retro focus type as a whole, it is suitable for a widening an image angle, as compared to a zoom lens system of a type in which a lens unit of a positive refracting power precedes.
As a conventional zoom lens system of a negative precedence type, a four-unit zoom lens system in which, a first lens unit having a negative refracting power, a second lens unit having a positive refracting power, a third lens unit having a positive refracting power, and fourth lens unit having a negative refracting power are disposed in order from the object side to the image side for achieving a magnification ratio of 4 or more at a zoom lens system of a negative precedence has been disclosed in Japanese Patent Application Laid-open Publication Nos. 2004-318107, 2004-318108, and 2007-156385.